Working out with PowerTOP what I can get from my h/w...

[Damon Hart-Davis]

Hi,

I sort of managed to build a custom kernel before, though was a  
little short of space on my (SD card) boot/usr area, and have never  
applied a whole patch set.

What I'm mainly concerned about is:

1) What's the risk of actually *damaging* something trying to force  
HPET and C3/C4?

2) What extra power savings might a reasonably expect as a  
percentage?  If, say, it is likely to be over 25% (eg 5W+) then it  
should be worth doing.

It's all about potential risk/reward!

(Oh, and I seem to have to repair some of *my* code in the NTP  
daemon, so, yes, I probably will try rebuilding it so I can provide  
stratum-1 service again, though it's a *long* way down the list of  
waker-upers... B^> )

Rgds

Damon

On 4 Aug 2007, at 16:24, Russell Harmon wrote:

> My suggestion here would be to make your own kernel. There are lots of
> patches that you can use (hpet, C3) to save power. Also, according to
> http://www.linuxpowertop.org/known.php#ntp NTP generates wakeups when
> it shouldn't. You should compile that from patched source and install
> yourself. Maybe have a look at http://www.linuxpowertop.org/known.php
> and see if there is anything else you can do.
>
> Personally, I find that gentoo can do almost all of that for me, so
> that is what i'd recommend for ease of use (it's what I use). If you
> already have a production system however, it's probably not worthwhile
> to redo it.
>
> On 8/4/07, Damon Hart-Davis <dhd at pop3.exnet.com> wrote:
>> [Sorry if this gets through twice: I messed up last time...]
>>
>> Hi,
>>
>> I have moved a whole bunch of servers off a rack of Solaris machines
>> and onto a single Linux laptop which I am trying to run on low-enough
>> power to run off solar PV for as much of the time as possible (see
>> http://www.earth.org.uk/low-power-laptop.html) and total power use
>> has come down from ~670W to <30W on mains (<20W powered from solar PV
>> via an efficient DC/DC converter).
>>
>> But I'm not sure how far further I can push the h/w I have.
>>
>> For example, it doesn't show C3 or C4 states available which is a
>> shame since it is 99% idle (most time is spent in C2).
>>
>> Also, it doesn't show HPET as being available, which results in ~50
>> extra wakeups per second.
>>
>> Now I *am* running a bunch of DNS, NTP, SMTP, and HTTP servers on
>> that (Core Duo T2250) machine, albeit quiet ones, that generate ~30+
>> wakeups per second themselves legitimately.
>>
>> Is it worth trying to force activate HPET, C3 ad C4?
>>
>> How can I safely do it if so?  I have looked at the BIOS with
>> dmidecode and biosdecode, and don't get any great clues.
>>
>> I have played with building a previous kernel but am now simply
>> running a stock (22-rc7) Ubuntu "Gutsy" kernel in my "Feisty" system.
>>
>> I am using cpufreqd/ondemand which I have tuned as good as I can get
>> (quick builds, idles in lowest freq ~99%).
>>
>> I am using laptop-mode.
>>
>> And of course I have used powertop to help tune userspace and
>> cpufreqd, which is why I am here!
>>
>> Rgds
>>
>> Damon
>>
>>
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>
>
> -- 
> Go read my blog: http://eatnumber1.blogspot.com/
>